Age Differences in Personality Among Elderly Medicare Patients Because of changes in health status and major life events such as the death of a spouse, one might expect to find changes in personality in the extreme old. Few studies on personality and aging have included participants aged 80 and older and only two previous studies used well-validated and comprehensive measures of personality. The purpose of this study was to determine whether the five factors of personality as measured by the NEO-FFI ? Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness, differed between frail, undereducated Medicare recipients aged 65-79 and those aged 80-100. Four of the five major personality factors showed no significant age differences between those under age 80 but 65 or older and those over 80. Only the Agreeableness versus Antagonism factor was higher in 80-100 year old participants. In addition the age difference of those over 80 compared to those under 80 was greater for males than females. The major implication of these cross-sectional findings is that, with the exception of a tendency to become more agreeable, there is little evidence to expect major differences in personality even among individuals in the last decades of life. This is an important finding as it highlights the stability of personality despite the likelihood that older individuals are undergoing several physical and cognitive changes. Hence, personality assessed earlier in life can still serve to inform geriatricians and psychiatrists of the vulnerabilities and strengths patients will possess even when they reach advanced old age. Longitudinal course of personality trait development in adulthood and old age Although the main outline of age changes in personality traits is known, many uncertainties remain. Developmental trends for Agreeableness and Conscientiousness are unclear, because these factors appear to increase with age in cross-sectional analyses, but do not increase in a large-scale longitudinal analysis. Even less is known about longitudinal trends for the specific traits or facets of the five factors. Little is known about age trends in extreme old age: The few studies that focus on this segment of the lifespan have found inconsistent results. There is a need to clarify and refine the description of the longitudinal course of personality trait development in adulthood. We examined age trends in the five factors and 30 facets assessed by the Revised NEO Personality Inventory in Baltimore Longitudinal Study of Aging data (N = 1,944; 5,027 assessments) collected between 1989 and 2004. Consistent with cross-sectional results, Hierarchical Linear Modeling analyses showed gradual personality changes in adulthood: a decline up to age 80 in Neuroticism, stability and then decline in Extraversion, decline in Openness, increase in Agreeableness, and increase up to age 70 in Conscientiousness. Although most facets showed curves similar to the factor they define, some did not, particularly within the Extraversion domain. Men and women showed similar curves and cohort effects were modest. The results of this longitudinal study are consistent with cross-cultural patterns of age differences observed in cross-sectional studies, supporting the view that these maturational trends are universal. The study of normative trends provides a reference point against which to examine individuals with distinct patterns, which might be due to genetic factors, life experience, or disease, such as Alzheimer?s disease or depression.